Shares of Celldex Therapeutics Inc. /zigman2/quotes/200895050/composite CLDX +1.82% soared 43.1% in premarket trading on Monday after the company shared positive data from an ongoing, open-label Phase 1b clinical trial for an experimental treatment for hives. Celldex said that 95% of participants diagnosed with two forms of chronic inducible urticaria reported a complete response to treatment and 5% had a partial response. The data was presented Friday during the European Academy of Allergy and Clinical Immunology Annual Congress. The study has 20 participants. The therapy is currently being tested intravenously but Celldex said it plans to begin testing a subcutaneous version of the drug in the third quarter. Celldex's stock has soared 84.9% this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -0.08% is up 16.3%.